The present invention relates to components and catalysts for the polymerization of olefins, as well as to specific diamines which can be used as electron donors in said catalysts.
Catalysts comprising titanium compounds supported on magnesium halides in active form are well known in the art. Catalysts of this type are described in U.S. Pat. No. 4,298,718, for example.
Although highly active both in the polymerization of the ethylene and .alpha.-olefins, such as propylene, said catalysts are not sufficiently stereospecific.
Stereospecificity has been improved by adding an electron-donor compound to the solid component comprising the titanium compound (U.S. Pat. No. 4,544,717).
Further improvements have been obtained by using both an electron-donor compound added to the solid component (internal donor) and one added to the Al-alkyl compound (external donor) (U.S. Pat. No. 4,107,414).
Very high performances, in terms of activity as well as stereospecificity, are given by the catalysts described in European patent no. 0045977. Said catalysts comprise an magnesium halide in active form as the solid component, on which is supported a titanium halide (TiCl.sub.4) and an electron-donor compound selected from specific classes of carboxylic acid esters, such as phthalates for example. The co-catalyst used is an Al-alkyl compound to which is added a silicon compound containing at least one Si-OR bond (R=hydrocarbon radical).
U.S. Pat. No. 4,522,930 describes catalysts whose solid catalyst component is characterized in that it contains an electron-donor compound which can be extracted by means of Al-triethyl (under standard extraction conditions) for at least 70% in moles and in that it has a surface area of at least 20 m.sup.2 /g after extraction.
Said catalysts comprise an Al-trialkyl compound as cocatalyst, to which is added an electron-donor compound (external donor) having the property of not causing complexing reactions with Al-triethyl, which reactions are detectable by potentiometric titration under well defined reaction conditions. The above mentioned electron-donor compounds comprise silicon compounds having Si--OR bonds; 2,2,6,6-tetramethylpiperidine, 2,2,5,5-tetramethyl-pyrrolidine, Al-diethyl-2,2,6,6-tetramethylpiperidide, Al-dichloromonophenoxy and other compounds.
Unexpectedly a new class of amines has now been found that are useful in the formation of catalysts and catalyst components for the polymerization of olefins. Namely, the amines of the invention have the property of providing highly active and stereospecific catalysts when used as internal donors, i.e. when they are present in solid catalyst components comprising a titanium halide, or a titanium halogen alcoholate, supported on magnesium halide in active form. The co-catalyst used is an Al-alkyl compound, optionally in combination with an electron-donor compound (external donor).
The above result is particularly surprising if one considers the fact that there are no known amines capable of giving good performances when used as internal donors.
Even when used as external donors, i.e. in combination with Al-alkyl compounds and solid catalyst components having the characteristics described in U.S. Pat. No. 4,522,930, the amines of the invention form highly active and stereospecific catalysts.